1. Field of the Invention
The invention is based on known ball seat valves for adjusting a flow of a fluid medium. Ball seat valves of this kind are used in many engineering fields in which it is necessary to adjust a flow of fluid media such as gases or liquids, for example in the field of hydraulic control units.
2. Description of the Prior Art
An important sample application for ball seat valves of this kind can be found in the field of automotive engineering, particularly in the field of injection technology. In numerous injection devices, ball seat valves are used for regulating hydraulic pressure and/or controlling the injection behavior of such systems. Primarily in the field of high-pressure reservoir injection systems (common rail systems), ball seat valves are used to control the lift of an injection valve closure member, which opens or closes injection openings. Examples of such devices are disclosed in DE 101 52 173 A1 and DE 196 50 865 A1. In them, a control chamber that directly or indirectly influences the lift of the injection valve closure member is connected to the ball seat valve directly via an inlet or through an additional bore. In addition to a valve ball, the ball seat valve has an actuator that presses the valve ball into a valve seat or lifts it away from the seat in order to disconnect or connect the control chamber from or to a relief chamber.
As is also demonstrated in DE 101 52 173 A1, for example, flow-adjusting ball seat valves known from the prior art generally have a choke valve on the side of the inlet oriented toward the control chamber. On its side oriented toward the ball seat valve, this choke valve is adjoined by one or more expansions of the inlet, which can assume various shapes.
In actual use, though, conventional ball seat valves known from the prior art have the disadvantage of a powerful erosion, particularly in the high-pressure reservoir injection systems functioning at pressures of several thousand bar. This erosion is in particular due to a cavitation in the choke valve, largely occurring outside the lift throttle limit. The expression “lift throttle limit” refers to the limit of the lift of the ball seat valve above which the flow no longer changes with a constant pressure upstream and downstream of the ball seat valve. As time passes, the above-described cavitation effects at the choke valve result in so-called cavitation erosion due to condensation, particularly in the seat region of the ball seat valve. As a result, a change occurs in the closing behavior of ball seat valves and this is accompanied by a change in the injection behavior of the injection device.